1. Field of the Invention
The present invention relates to a control system, and more particularly, to an LED control system.
2. Description of Related Art
In recent years, Light Emitting Diode (LED) has been widely used in various lighting applications. The power for lighting an LED is provided by a power source. Currently, the power applied to the LED is regulated by a certain regulation circuit, e.g. an LDO (Low-dropout) circuit, a buck circuit, a boost circuit, a fly-back circuit, a SEPIC (single-ended primary-inductor converter) circuit, or a CUK circuit to prevent the LED from being damaged by the excess power provided by the power source.
FIG. 1(A) shows a typical LDO circuit for a voltage source. As shown in FIG. 1(A), a voltage source 10 is connected to an LED 20. The LED 20 is connected in series with a transistor 31 on a current path. An operational transconductance amplifier (OTA) 30 changes the resistance of the transistor 31 to regulate the LED current. Besides, the buck circuit, boost circuit, fly-back circuit, SEPIC circuit, or CUK circuit can also provide the same effect.
However, if a regulation circuit for a voltage source is connected to a current source, the regulation circuit may not operate normally. FIG. 1(B) shows a typical LDO circuit suitable for a voltage source but connected to a current source. As shown in FIG. 1(B), if current source 10 provides more current than desired, although the resistance of the transistor 31 is changed, the un-consumed current generates the extra high voltage on the drain of transistor 31 and could damage the transistor 31. Similarly, if a regulation circuit suitable for a current source is connected to a voltage source, an erroneous current will be consumed on the regulation circuit. As a result, the LED or the regulation circuit is likely to be damaged if an incorrect regulation circuit is used.
Therefore, there is a need to provide an improved LED control system capable of detecting whether the regulation circuit in operation is suitable for the type of power source in operation in order to solve the aforementioned problem.